Inhalers intended for medicaments in powder form are known to the art. EP No. 0069715 describes and illustrates one such device in which the powder is metered in given dosages through apertures located in a rotatable disc, these apertures being introduced into an airduct or channel through which air is inhaled, by rotating the disc. A characteristic feature of this type of inhaler is that it is used to administer a precise amount, or dosage, of highly potent medicaments, which are consequently metered in extremely small amounts, for example 0.1 mg. The stored amount of medicament is also kept small, for example 10-30 mg. Such a small quantity, and the change therein, cannot readily be discerned by direct observation. In this case there is a risk of the supply of medicament becoming exhausted without the patient noticing the fact in time, which results in the patient missing his/her treatment with the subsequent risk to the wellbeing of the patient. Consequently, there is a need for an indicator which will readily indicate a number of dosages administered in a clear and unambiguous fashion.
The need for indicating the number of dosages measured in the aforesaid minute quantities of medicinal substances is also found in dosage dispensing devices other than dosage inhalers.